This invention relates to apparatus and methods for assaying and monitoring radioactive contaminated materials such as clothing, wipe rags, bags and the like which are of a combustible nature and had been accumulated in a large container (box) for purposes of processing to recover the fissile and/or fertile materials.
It has long been recognized in the nuclear field that control must be exercised over fissile and/or fertile materials. The control is essential to safeguard the health and well-being of individuals who work with nuclear materials as well as to prevent the acquisition of such materials by an individual or group of individuals who may be desirous of constructing nuclear devices and/or weapons. Control is also necessary because of the intrinsically high monetary value of this material. The apparatus hereinafter defined is generally directed to the materials of uranium 235 and uranium 238 although the same may be utilized with materials such as plutonium or the like.
In implementing the invention disclosed herein provision is first made for the deposition of the hereinbefore referred to materials in a container or box which may in one embodiment be approximately 4 feet in height, 4 feet in width and 4 feet in depth preferably constructed of combustible material such as wood or cardboard. The combustible box is delivered by means of a forklift truck or other conveyance to a first motorized conveyor by means of which it is moved into a monitor wherein measurements are made first in a passive mode (without an interrogation neutron source) and then in an active (with an interrogation neutron source) mode. Dependent upon such measurements the box is then moved out either onto a reject queue or a burn queue. The box or boxes on the burn queue are passed into an incinerator via the burn queue and the box and contents are then incinerated and the residue is passed out through the incinerator outlet to a collector can. The collector ash can and contents are then placed upon a queue and propelled on said queue to a further monitor station. The monitor station for large containers provides a means for measuring the uranimum content of both uranimum 235 and uranium 238 and of the combustible waste contained in the box. The heretofore measurements are made by detecting the neutrons and gamma rays from the uranimum both with and without a neutron interrogation source activity. Because of the importance of these measurements to the control of nuclear criticality the measurement of fissile and/or fertile content are both performed in two diverse measurements each of which is redundant.